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YACS (Yet Another Calibration Square

by Paciente8159 Oct 1, 2017
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What are the dimensions of the YACS.STL model measuring AC, BD, and AD? Just trying to have those measurements as a cross reference to my prints.

YACS is shaped as a 100mm by 100mm square so AB and BD are 100mm.
The theoretical diagonal AC is given by the Pythagorean theorem:
AC = SquareRoot(AD^2 + BD^2)
In this case it's aprox. 141,42mm

How do I measure it?...How schould I put my caliper? From the corner or between 2 corners?

Ok, can someone help my dyslexic ass. I'm looking at the diagram. Could someone please specifically say which side the A, B, C, D is suppose to reference to? Left, right, front, back. Am I suppose to align it to marlin logic?


i did print the horizontal one, but the vertical one i cant do.

about 50% up the nozzle catches on the crossing parts

i know they are there to keep the distance between the 2 outer pillars, but would it be possible to make a version without the cross?

I added a new vertical print part. Hope it helps.

tested the org. vertical model to check what goes wrong

about 45% in the to print the nozzle hits the 2 "arms" that goes diagional and i have even upgraded to a stronger part cooling fan

i took off the print and discovered that the 2 outer beams bend ever so slightly outwards and this lifts up the crossing parts in the middle enough that nozzle catches

i 'm now trying to print the alternative version and see if it helps, if not i will try and make the crossing part solid

thanks, will give it a go in afew days, going to upgrade heatblock and nozzle

Marlin 1.1.8 Bed Skew Compensation - How To - 2018 - Chris's Basement

Many thanks for your sharing. This model fixed my printer's skew problem a lot ^^

Very nice. I'm assuming that I need to print two verticals. One for XZ and one for YZ.
Two questions:

  1. What alignment should be used printing on the YZ axis? Should "A" be toward the rear of the printer or toward the front?
  2. Is the diagonal measurement on the vertical square (A to C and B to D) from the notch to the corner or corner to corner?


Did you ever get an answer. You have a very valid question.

Not specifically. But the Marlin FW does contain the instructions. These are from Marlin 2.0 Configuration.h Bed Skew Compensation.

 * Bed Skew Compensation
 * This feature corrects for misalignment in the XYZ axes.
 * Take the following steps to get the bed skew in the XY plane:
 *  1. Print a test square (e.g.,
 *  2. For XY_DIAG_AC measure the diagonal A to C
 *  3. For XY_DIAG_BD measure the diagonal B to D
 *  4. For XY_SIDE_AD measure the edge A to D
 * Marlin automatically computes skew factors from these measurements.
 * Skew factors may also be computed and set manually:
 *  - Compute AB     : SQRT(2*AC*AC+2*BD*BD-4*AD*AD)/2
 * If desired, follow the same procedure for XZ and YZ.
 * Use these diagrams for reference:
 *    Y                     Z                     Z
 *    ^     B-------C       ^     B-------C       ^     B-------C
 *    |    /       /        |    /       /        |    /       /
 *    |   /       /         |   /       /         |   /       /
 *    |  A-------D          |  A-------D          |  A-------D
 *    +-------------->X     +-------------->X     +-------------->Y

As you can see from the graphics at the end:

XY: "A" is front left.
XZ: "A" is to the left.
ZY: "A" is to the front.

YACS (Yet Another Calibration Square


  1. Align it in the same direction as your axis. For XZ the wider side should be on the X axis. This means that if you look in the Y should see the hole frame (front and the X in the middle).
  2. Corner to corner. The notch on the top is aligned with the corner to provide a better base for the caliper and easier to get the diagonal right.

@paciente you don't speak english do you????

@artieH the letters face the front.

You're bashing an answer from almost a year ago. I answered it myself, back then, but it no longer matters. I'm not using Marlin's skew compensation and now use Marlin's Auto Calibrate and the Calibration Tool by Coffea to adjust the Diagonal Rod length.

Kossel / Delta Dimensional Calibration with Instructions
by Coffea

i see no such answer. not to mention this is still used to this answer is not just for you.
the tool you mentioned only works for delta anyway

This was created to be used with Marlin skew compensation (check Marlin's Configuration.h file in the section Bed Skew).
Resuming measure both diagonals and side AD.

You can compute the skew angle by using these equations:

Comments deleted.

Measuring A<>D I take it we measure from the long edges and not the protruding nubs used for A<>C and B<>D measurements?

Thanks, I will give this a try with Marlin 1.1.8 - I just need to remove the springs under my heatbed and replace with solid spacers so I don't have variance coming in to things there.

ok.... now how do we use this dohicky??????

Wow this referenced in Marlin 1.1.7 to measure for Bed Skew Compensation - Nice. I have to try it

I was re-configuring my D-Bot firmware and saw this as well. Very nice!